README: use latest container tag in the examples

We recently changed the container tags from vNN to gSHA-1, but we didn't
update README.md. Also, we now push `latest`, which is always updated,
so use this tag in the examples and mention to look at CONTAINER_VERSION
in .buildkite/autogenerate_pipeline.py for a specific version.

Reported-by: Hanna Czenczek <[email protected]>
Signed-off-by: Stefano Garzarella <[email protected]>

Author: stefano-garzarella

README.md

@@ -163,7 +163,7 @@ steps:
     platform: x86_64.metal
   plugins:
   - docker#v3.8.0:
-      image: rustvmm/dev:v16
+      image: rustvmm/dev:latest
       always-pull: true
   timeout_in_minutes: 5
 ```
@@ -244,14 +244,15 @@ coverage before submitting a PR, run the coverage test:
 
 ```bash
 CRATE="kvm-ioctls"
-# NOTE: This might not be the latest container version, you can check which one we're using
-# by looking into the .buildkite/autogenerate_pipeline.py file.
-LATEST=16
+# NOTE: `latest` should point to the latest version, but you can specify an exact
+# one as we do with CONTAINER_VERSION in .buildkite/autogenerate_pipeline.py file.
+TAG="latest"
+docker pull rustvmm/dev:${TAG}
 docker run --device=/dev/kvm \
            -it \
            --security-opt seccomp=unconfined \
            --volume $(pwd)/${CRATE}:/${CRATE} \
-           rustvmm/dev:v${LATEST}
+           rustvmm/dev:${TAG}
 cd ${crate}
 pytest --profile=devel rust-vmm-ci/integration_tests/test_coverage.py
 ```
@@ -292,7 +293,7 @@ steps:
     platform: arm.metal
   plugins:
   - docker#v3.8.0:
-      image: rustvmm/dev:v16
+      image: rustvmm/dev:latest
       always-pull: true
 ```
 
@@ -330,11 +331,15 @@ pipeline output. In its present form, the test cannot fail.
 To run the test locally:
 
 ```bash
+# NOTE: `latest` should point to the latest version, but you can specify an exact
+# one as we do with CONTAINER_VERSION in .buildkite/autogenerate_pipeline.py file.
+TAG="latest"
+docker pull rustvmm/dev:${TAG}
 docker run --device=/dev/kvm \
            -it \
            --security-opt seccomp=unconfined \
            --volume $(pwd)/${CRATE}:/${CRATE} \
-           rustvmm/dev:v${LATEST}
+           rustvmm/dev:${TAG}
 cd ${CRATE}
 pytest rust-vmm-ci/integration_tests/test_benchmark.py -s
 ```
@@ -351,14 +356,15 @@ that autogenerates the pipeline. For example:
 ```bash
 cd ~/vm-superio
 CRATE="vm-superio"
-# NOTE: This might not be the latest container version, you can check which one we're using
-# by looking into the .buildkite/autogenerate_pipeline.py file.
-LATEST=16
+# NOTE: `latest` should point to the latest version, but you can specify an exact
+# one as we do with CONTAINER_VERSION in .buildkite/autogenerate_pipeline.py file.
+TAG="latest"
+docker pull rustvmm/dev:${TAG}
 docker run -it \
            --security-opt seccomp=unconfined \
            --volume $(pwd):/${CRATE} \
            --volume ~/.ssh:/root/.ssh \
-           rustvmm/dev:v${LATEST}
+           rustvmm/dev:${TAG}
 cd vm-superio
 ./rust-vmm-ci/test_run.py
 ```